sql 判断连续数字

设表名为TABLENAME,字段名为FIELD1则：
SELECT
	FIELDN = FIELD1 
FROM
	TABLENAME 
WHERE
	NOT EXISTS (
SELECT
	FIELD1 
FROM
	TABLENAME A 
WHERE
	A.FIELD1 = tablename.field1 + 1 
	) UNION
SELECT
	FIELDN = FIELD1 
FROM
	TABLENAME 
WHERE
	NOT EXISTS (
SELECT
	FIELD1 
FROM
	TABLENAME A 
WHERE
	A.FIELD1 + 1 = tablename.field1 
	) 
ORDER BY
	FIELDN